Analyzers are known which automatically process a test element, sometimes labeled a "slide", that has all of the necessary reagents in a dried format, so as to generate a signal indicative of the concentration of an analyte of a body liquid. Such analyzers include a station for supplying test elements, a station for dispensing an aliquot of body liquid, such as serum, onto a test element, a station for incubating a test element containing that aliquot, a station for detecting the signal produced by the test element, and means for moving such test element between such stations. Examples of such analyzers are shown in U.S. Pat. Nos. 4,539,855 and 4,568,519 issued on Sept. 10, 1985 and Feb. 4, 1986, respectively.
In such analyzers, particularly in the portion doing rate analysis wherein the rate of change in signal generated by the test element is measured, the incubating station keeps the test element(s) for the entire incubation, so that each such element is not removed therefrom until all readings are completed. That is, after the final reading, preferably a photometric reading, is taken, a test element in such an incubator is picked out of the incubator and dropped into a disposal bin. A useful construction of an incubator and picker capable of this function is shown in FIGS. 2 and 2a of the aforesaid U.S. Pat. No. 4,568,519.
Such a construction does not make it possible to easily wash the test element with, e.g., water, after partial incubation and prior to a first reading at the read station. (Such a wash step is useful in certain assays, such as immunoassays, to separate reaction product, e.g., complexed antibody and antigen, from unreacted reagent, e.g., antibody or antigen not yet complexed.) That is, the logical step would be to add wash liquid to the test element through the top of the incubator, while the test element remains in the incubator. Such analyzers are in fact known in the industry. However, the incubator is constantly rotating the test elements, even while making photometer readings, in order to make 10 or so readings per minute as is needed for accurate rate analysis. The only stoppage occurs for two seconds for loading and unloading test elements. It is not feasible to try to wash test elements "on the fly" in such an incubator.
Thus, prior to this invention there has been an unsolved need to provide a wash station in an automated analyzer for allowing the washing of a test element to force separation of reaction product and unreacted reagent. This need particularly has not been met for use with an incubator in which the test elements are constantly rotating therein except when being loaded and unloaded.